Applicant currently markets a livestock head holder of the aforementioned type, which is illustrated in FIG. 1. Top and bottom closing members respectively act against the top and bottom of the animal's neck to hold the animal's head in place, for example to restrain the animal's head during ear tagging, oral examination (mouthing), etc. The head holder features a frame 10 mounted to the head gate of a squeeze chute (not shown), and a linkage in which the two holding members 12, 14 are connected by an intermediate link 16 and moved via an operating lever 18. The operating lever 18 is affixed to the bottom holding member 12 to reach outward therefrom at a first end 12a thereof opposite a U-shaped neck-cradle 20 that is carried at an opposed working end 12b of the bottom holding member 12 to fit against the underside of the animal's neck.
The drawing shows the prior art head holder apparatus in a closed state in which both holding members span laterally outward from the frame in a common direction so that the cradle 20 of the bottom holding member resides below the top holding member 14 near the working end 14b thereof in an orientation opening upwardly theretoward. The operating lever 18 is used to transition to the apparatus to this illustrated closed state from an initially opened state in which the top and bottom holding members instead reach upward and downward from the top and bottom of the frame in nearly vertical orientations. To perform the closing stroke that transitions the linkage from the open state to the closed state, the free end 18a of the operating lever 18 pulled downwardly from its initial position reaching upward from the first end of the upright bottom holding member. This swings the bottom holding member 12 into the laterally reaching orientation of the illustrated closed state to brace the attached neck-cradle 20 against the underside of the animal's neck. During this closing stroke of the head holder, the intermediate link 16 causes the top holding member 14 to simultaneously swing down against the topside of the animal's neck, thereby firmly holding the neck in a stationary position between the holding members 14, 16 to restrain head movement of the animal.
So that exertion of force against the holding members by attempted movement by the animal will not open the head holder, a lock and release mechanism 22 automatically locks the linkage to block movement thereof in a reverse opening stroke that would otherwise allow the holding members to move away from one another toward the opened state. The lock and release mechanism 22 features a shaft 24 whose lower end is pivotably pinned to the bottom holding member 12. The shaft 24 passes upwardly through a lock housing 26 carried on a mounting plate 28 that is pivotably pinned to the top end of the frame 10. Inside the lock housing 26, the shaft 24 passes through an opening in a locking plate that is spring-biased into a tilted locking position in which the perimeter edge of the plate's opening bites against the periphery of the shaft to lock the shaft against upward movement through the lock housing 26. This locks the linkage against opening, as the opening stroke requires lifting the free end of the operating lever, would in turn attempts to force the shaft 24 upwardly. The locked state of the shaft 24 prevents such upward movement, thus preventing the operating handle from being lifted to initiate the opening stroke.
Opening of the head holder thus requires temporary release of the locking action, which is achieved by pulling upward on a release pin 30 that projects upwardly out of the lock housing 26 at the upper end thereof. Inside the lock housing, one end of the locking plate is pivotably supported between a pair of locating pins 36 that cross horizontally through the lock housing, while the other end of the lock plate engages with a circumferentially-recessed reduced-diameter area of the release pin 30. As a result, manual lifting the release pin 30 overcomes the resistance of a spring that is coiled around the release pin 30 between the top wall of the housing and the locking plate in order to raise this pin-engaged end of the locking plate. This lifting of the release pin 30 thus straightens out the locking plate into a lock-releasing position perpendicular to the shaft, whereupon the shaft can slide freely through the opening in the lock plate.
From the forgoing, it will be appreciated that the prior art head holder requires two separate input actions by the operator in order to open the apparatus, namely manual lifting of the release pin 30 to release the locked state of the linkage, and a separate lifting of the operator lever 18 with the other hand to perform the opening stroke.
It would be desirable to provide a livestock head holder with a simplified unlock and opening procedure.